Kidney stones (renal lithiasis, nephrolithiasis)

What are kidney stones?

Renal lithiasis / nephrolithiasis (renal / nephro = [in relation to] kidney + lithiasis = stone) are the names of a condition most commonly known as kidney stones, which is characterised by hard deposits (made up of salts and minerals) that form inside the kidneys (two bean-shaped organs situated on both the left and right side of the body).

Most often, these hard deposits, which are generally pebble-like in appearance, resembling polished river-rocks (brownish yellow in colour, and may have either a smooth or rough texture), form when urine in the body becomes concentrated (i.e. during dehydration when there is too little water in the urine), and salts and minerals crystallise and clump together. These hard and crystallised deposits (known as renal calculi) can then affect any portion of the urinary tract between the kidneys and the bladder, including the ureters (tubes that carry urine from the kidneys to the bladder) and urethra (a tubular structure that moves urine to the outside of the body). When kidney stones occur within the urinary tract, this is known as urolithiasis, and when these are situated in the ureters, this is referred to as ureterolithiasis.

The kidneys serve as the body’s filtering system for blood, as well as for the removal of waste products (in the form of urine). During the filtration process, the kidneys help to regulate electrolyte levels in the body which aid various functions. Waste (urine), once filtered, drains from the kidneys through the ureters (narrow tube structures) and into the bladder. Urine then fills the bladder creating a ‘need to urinate’ (i.e. excretion of liquid from the body) and when released, is emptied to the outside of the body through the urethra (a wider tube structure).

Kidney stones which form are tiny to begin with (i.e. smaller than a grain of sand), but gradually grow, increasing in size. For doctors and patients alike, determining the size of a kidney stone is very important, as is its location within the system. A stone that is located within the kidney is very rarely painful. Symptoms of pain are more commonly associated with stones that are located within the ureter. This is because a stone causes a blockage, and while the kidneys continue to filter and produce urine, a build-up of pressure behind the crystallised deposit occurs, resulting in swelling of the kidneys. Pressure causes pain, but also tends to ‘push the stone along’ to a point where it can be passed via the bladder.

It can be fairly painful to pass a kidney stone (without medical intervention), but this is preferred to medical means of removal. If hard deposits become lodged somewhere along the urinary tract, infection and other complications can occur, which will require surgery to resolve.

In the case of kidney stones, preventative measures are most often better than cure. Avoiding various factors which can result in the formation of these hard deposits can dramatically reduce a person’s risk of experiencing recurrent kidney stones.